Cyclic manufacture of potassium carbonate



Nom l2, 1935..

F. RSBERG GYYCLIG MANUFACTURE OF' POTASSIUM GARBONATE Filed Aug. lO, 1932 Patented Nov. 12, 1935 UNITED STATESl PATENT Germany, assigner to OFFICE CYCLIC MANUFACTURE OF POTASS'IUM 1 CARBONATE Friedrich Rsberg, Berlin -Niederschoneweide,

Kali-Chemie, Aktiengesellschaft, Berlin, Germany Application August 10, 1932, Serial This invention In Germany September 29,` 1931 2 Claims.

relates to the manufacture of potassium carbonate from potassium salts of strong mineral acids and magnesium carbonate trihydrate.

It is known to make treating with carbon dioxide solution of potassium chloride, water containing double salt of bonate and magnesium carbon salt, precipitates, water at raised temperature fur potassium carbonate by a suspension of trihydrate in an aqueous whereby a crystal potassium bicarate, named Engel which on decomposition with nishes an aqueous solution of potassium bicarbonate, which may contain potassium carbonate and solid magnesium bicarbonate trihydrate, which is used again for the manufacture of potassiu fresh potassium chloride. Th

m carbonate from is process, which is called Engel-Precht method, is supposed to take place according to the followin g equations:

It will be seen from the equations, thatone third of the magnesium carbonate trihydrate employed for the manufacture of Engel salt is consumed and converted into magnesium chloride,

which is removed from the process.

The other two thirds of magnesium carbonate trihydrate employed as starting material are recovered and are used again for the manufacture of Engel salt.

When working in a cycle, which is the rule in of Engel salt and to employ disadvantage, with Engel salt, crease the yield ties in the preparation, of the Engel salt. magnesium carbonate, which i this mixture for of fresh Engel salt. This prothat sludges are which sludges dein double salt and make difliculseparation and handling Moreover the trihydrate of s used in a cycle has to be regenerated very often due to the presence of these sludges.

'I'he Engel-Precht method consists in treating with carbon dioxide a suspension of magnesium carbonate trihydrate in an aqueous solution of potassium chloride thereby forming Engel salt, that is crystal Water containing double salt of potassium magnesium carbonate, and ma bicarbonate and gnesium chloride,

decomposing the precipitated Engel salt with Water at raised temperature and thereby forming magnesium carbonate trihydrate and potassium bicarbonate, separating out solid magnesium carbonate trihydrate, suspending the said trihydrate again in an aqueous solution of potassium chloride and repeating the treatment with carbon dioxide in the same manner as in the beginning of the process.

The main object of the invention is to provide for a cyclic method for making potassium carbona-te according to Engel-Precht, in Which'the formation of sludges in the preparation of` Engel salt, being an intermediate product, is reduced.

A further object of the invention is to provide for a method, by which a frequent regeneration oftrihydrate of magnesium carbonate obtained by decomposition of Engel salt is avoided.

Investigations have shown, that the formation of sludges in the manufacture of Engel salt with a mixture of fresh magnesium carbonate trihydrate and magnesium carbonate trihydrate recovered by decomposition of Engel salt is to a great extent due to the presence of small process. A magnesium carbonate trihydrate free from these impurities, such as a trihydrate, which has already been used in the cyclic process, forms much less sludge, which basic magnesium compounds and the impurities of the fresh trihydrate.

According to the invention the formation of sludges in the preparations of Engel salt in the cyclic manufacture of potassium carbonate according to Engel-Precht is reduced, by carrying out separately the preparation of Engel salt with the amount of fresh magnesium carbonate trihydrate necessary for completion from the manufacture of the same double salt with the magnesium carbonate trihydrate obtained by decomposition of Engel salt in a previous operation. The Engel salt obtained by the two operations may be decomposed separately or together and the magnesium carbonate trihydrate obtained by this decomposition or these decompositions is then employed together for the manufacture of fresh Engel salt, Whereas the fresh magnesium carbonate introduced into the process is used for a separation preparation of Engel salt. By this separate preparation of Engel salt with fresh magnesium carbonate trihydrate the greatest part of the impurities present in the fresh trisludge.

hydrate is removed with the magnesium chloride from the process, thus decreasing the formationof sludge in the whole process. This separate preparation of Engel salt with fresh trihydrate may be considered as a purication of fresh trihydrate 'over the Engel-Precht process for the manufacture of potassium carbonate.

Examples 1. 1000 kg. of Engel salt with 13% MgO and 20% K2CO3 are prepared by treating with carbon dioxide a suspension of about 1450 kg. of magnesium carbonate trihydrate, obtained by decomposition of Engel salt with water in previous operations, in an aqueous solution of potassium chloride. There is practically no formation of On decomposing the 1000 kg. of Engel salt with water at temperatures between 40 and C. about 905 kg. of magnesium carbonate trihydrate with about 13,8% MgO are obtained as solid residue.

560 kg. of Engel salt with 13,5% MgO and 21,5% KzCOa are prepared by treating with carbon dioxide a suspension of about 800 kg. of fresh magnesium carbonate trihydrate, obtained by treatment of hydrated magnesia with carbon dioxide or by precipitating magnesium chloride solution with ammonium carbonates, in an aqueous solution of potassium chloride. There is only Very little sludge formation. On decomposing the 560 kg. of Engel salt with water at temperatures between 40 and 90 C. about 535 kg. of magnesium carbonate trihydrate with about 14% of MgO are obtained.

The trihydrate obtained in the rst decomposition step is added to the trihydrate obtained in wthe second decomposition step ,and the 1450 kg. of'trihydrate are employed for the manufacture of about 1000V kg.. of Engel salt as described in the first paragraph of the example. There is practically no sludge formation. Fig. l of the drawing illustrates the steps of the process.

2. 1000 kg. of Engel salt as in Example 1 are added to 560 kg. of Engel salt obtained from.

fresh trihydrate of magnesium carbonate. The mixture is decomposed with water at temperatures between 40 and 90 C. and about 1460 kg. of

trihydrate of magnesium carbonate with about 13.8% of MgO are obtained as solid residue. This Y residue is employed for the manufacture of about 1000 kg. of Engel salt practically without sludge formation. These 1000 kg. of Engel salt are mixed with 560 kg. of Engel salt prepared separately from fresh magnesium carbonate trihydrate and the mixture is decomposed as described above. Fig. 2 of the drawing illustrates the steps of the process.

Instead of potassium chloride in the examples other potassium salts of strong mineral acids such as potassium sulfate may be employed.

The foregoing detailed examples have been given for clearness of understanding only,` and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible in view of the prior art.

1. In the cyclic manufacture of potassium carbonate from potassium chloride by the Engel- Precht method, the improvement of compensating the magnesium carbonate trihydrate spent in the manufacture of Engel salt in the cycle by introduction of corresponding amounts of Engel salt into the cyclic process and of decomposing said introduced Engel Engel salt produced in the cycle and introducing the regenerated magnesium cycle.

2. In the cyclic manufacture of potassium carbonate from potassium chloride by the Engel- Preoht method, the improvement of compensating the magnesium carbonate trihydrate spent in the manufacture of Engel salt in the cycle by introduction into the process of fresh magnesium carbonate trihydrate produced in a non-cyclic process, the steps of separately converting the magnesium carbonate trihydrate regenerated in the cyclic process and fresh magnesium carbonate trihydrate into Engel salt, uniting the two batches of Engel salt, with water .at raised temperature and introduc-y ing the regenerated magnesium carbonate tri'- hydrate into the cycle.

FRIEDRICH RSBERG.

carbonate into the decomposing the Engel saltV salt together with the 

